Nutrition in Burn Patients

INTRODUCTION

The response to injury, known as hypermetabolism, occurs most dramatically

following severe burn. Increases in oxygen consumption, metabolic rate, urinary

nitrogen excretion, lipolysis and weight loss are directly proportional to the size of

the burn.1 This response can be as high as 200% of the normal metabolic rate, and

returns to normal only with the complete closure of the burn wound.2 There is

debate regarding the pathogenesis of this hypermetabolic state, but the general

consensus is that inflammation associated with the burn wound, heightened

cortisolemia, and the increased adrenergic activity seen in these patients are all

important factors.

Because the metabolic rate is so high, energy requirements are immense. These

requirements are met by mobilization of carbohydrate, fat, and protein stores.

Since the demands are prolonged, these energy stores are quickly depleted, leading

to loss of active muscle tissue and malnutrition. This malnutrition is associated

with functional impairment of many organs, delayed and abnormal wound

healing, decreased immunocompetence, and altered cellular membrane active

transport functions. Malnutrition in burns can be subverted to some extent by

delivery of adequate exogenous nutritional support. The goals of nutrition support

are to maintain and improve organ function, prevent protein-calorie malnutrition,

and improve outcomes.

Supporting the burn patient with adequate energy sources is paramount to

good outcome. Important topics in this regard are:

1. calculation of the caloric needs,

2. composition of the nutritional supplements and

3. means by which these nutrients are delivered

CALCULATING CALORIC NEEDS

Caloric requirements in adult burn patients are calculated using the Curreri

formula, which calls for 25 kcal/kg/day plus 40 kcal/% TBSA burned/day.1 This

formula provides for maintenance needs, plus the additional caloric needs of the

burn wounds. As an example, a 100 kg man with a 50% TBSA burn would require

2500 kcal for maintenance needs plus an additional 2000 kcal for burn related

metabolism. Therefore, he would require 4500 kcal/day that would be delivered

throughout the hospital course until the wounds were healed.

In children, formulas based on body surface area are more appropriate3,4 because

of the greater body surface area per kilogram. We recommend the following

formulas depending in the child age (Table 6.1). The formulas change with age

based on the body surface area alterations that occur with growth.

DIETARY COMPOSITION

The composition of the nutritional supplement is also important. The optimal

dietary composition contains 1-2 gm/kg/day of protein, which provides a

calorie to nitrogen ratio at around 100:1 with the above suggested caloric intakes.

This amount of protein will provide for the synthetic needs of the patient, thus

sparing to some extent the proteolysis occurring in the active muscle tissue.

Some amino acids are conditionally essential for these critical patients.

Glutamine is an important fuel for rapidly dividing cells such as enterocytes, lymphocytes

and macrophages. Recently, it has been demonstrated that supplemental

glutamine prevents deterioration in gut permeability and preserves mucosal structure

avoiding bacterial translocation in animal models of injury. Arginine is an

amino-acid which has been associated with accelerated wound healing, and supplemental

amounts up to approximately 2% of the total calories is recommended.

These amino acids are present in most enteral formulas, and it remains to be determined

whether further supplementation above these concentrations is of benefit.

Table 6.1. Formula for caloric calculations in children used at SBI

Age group Maintenance fluids Resuscitation fluids

(burn wound needs)

Infants (0-12 mos.) 2100 kcal/TBSA/24 h 1000 kcal/TBSA

burned/24 h

Children (1-12 years) 1800 kcal/TBSA/24 h 1300 kcal/TBSA

burned/24 h

Adolescents (12-18 years) 1500 kcal/TBSA/24 h 1500 kcal/TBSA

burned/24 h

Nonprotein calories can be given either as carbohydrate or as fat. Carbohydrates

have the advantage of stimulating endogenous insulin production, which

may have beneficial effects on muscle and the burn wounds as an anabolic hormone.

In addition, fatty liver is commonly seen after severe burns, which may be

related to diet. It has been shown recently that almost all of the fat deposited in the

liver is derived from peripheral lipolysis and not from de novo synthesis of fatty

acids in the liver from dietary carbohydrates. In fact, the likely cause for fatty infiltration

is relative inefficiency of hepatic transport of delivered fat. For this reason,

we prefer to use a carbohydrate based feeding in order to decrease the amount of

fat that the liver must handle. Currently we use Vivonex TEN® as our standard

tube feeding which contains mainly carbohydrates and virtually no fat.

A number of vitamins and trace materials (vitamins A, C, E, zinc, folic acid

and iron) are added because of their significant functions: free radical scavengers,

enhancing the immune response, and accelerating wound healing. See Table 6.2

for supplemental recommendations at Shriners Burns Hospital.

DIETARY DELIVERY

The diet may be delivered in two forms, either enterally through enteric tubes,

or parenterally through intravenous catheters. Parenteral nutrition may be given

in isotonic solutions through peripheral catheters or with hypertonic solutions in

central catheters. In general, the caloric demands of burn patients prohibit the use

of peripheral parenteral nutrition. In addition, total parenteral nutrition (TPN)

Table 6.2. SBI vitamin and mineral supplementation

0-12 years of age

Liquid or Chewable Multivitamin 1 dose q.d.

Ascorbic acid 250 mg q.d.

Folic acid 1 mg q. m.w.f.

Vitamin A

<>

2-12 years, 5000 IU

Zinc sulfate

<>

2-12 years, 110 mg q.d.

Vitamin E 5 mg q.d.

12 years or older

Adult Multivitamins q.d.

Folic acid 1 mg q. m.w.f.

Vitamin A 10000 IU q.d.

Zinc sulfate 200 mg q.d.

Vitamin E 10 mg q

delivered through a central vein has been associated with increased complications

(i.e. sepsis, thrombophlebitis, death) and currently is almost abandoned in our

hospitals. Herndon and others showed that in 30 burn patients randomized to

receive either TPN or enteral feedings (milk) mortality was 40% higher in the

TPN group, indicating that TPN increased mortality in these patients. TPN is

reserved only for those patients who cannot tolerate enteral feedings.5,6

In burn patients as well as in most of the critical care patients, enteral feedings

are recommended over parenteral feedings, other advantages are:

1. More physiologic and less costly

2. Maintains gut structure and function, may help prevent the translocation

of bacteria and/or toxins7

3. Blunts the hypermetabolic response to injury

4. Associated with decreased incidence of sepsis.

Enteral feeding has been associated with some complications, however, which

can be disastrous. Careful attention to detail is important in order to avoid their

presence. In general these complications can be divided into:

1. Mechanical complications (aspiration pneumonia, sinusitis, nasoalar,

esophageal and gastric mucosal irritation and erosion, tube lumen obstruction)

2. GI complications (diarrhea, fecal impaction)

3. Metabolic complications (dehydration, hyperglycemia, hyper- or hyponatremia,

hyper or hypophosphatemia, hypercapnia, hyper or hypokalemia)

Although gastric ileus is somewhat common, the small intestinal component

is rarely seen, therefore the gastrointestinal tract past the pylorus can be used for

administration of feedings. We recommend early feeding through nasoduodenal

tubes. Most of our patients begin feedings within 6 h after burn, at a low rate

(10-30 cc/h) and advancing as tolerated to meet caloric needs while reducing IV

fluids accordingly. Tube feedings are continued throughout the hospital course at

calculated rates until the wounds are healed.

All of our patients receive both nasogastric and a nasoduodenal tubes. The

gastric tube is initially used to decompress the stomach. Then after the first burn

wound excision it is used to provide a low rate of feeding to the stomach (30 cc/h)

as a buffer, decreasing the incidence of peptic ulcer disease and erosive gastritis. It

is also used to check gastric residuals every hour, so as to avoid gastric distention

with its risk of aspiration. Gastric pH is checked hourly with the addition of antacids

(Maalox, Mylanta) to maintain pH > 4.5. Nasoduodenal tubes are placed

alongside the nasogastric tube to deliver most of the tube feedings. The feeding

through this tube is continuous at a rate to meet the caloric needs. Nasoduodenal

tubes are notoriously difficult to place. See Table 6.3 for suggestions in successful

placement.

Many commercial feeding solutions are available, although whole bovine milk

is a viable alternative. Milk is nutritionally balanced, inexpensive, easily available,

and well tolerated. Potassium requirements are met, but sodium (25 mEq/L) needs

to be supplemented. Infants under one year of age, are normally fed with commercial infant formulas to meet calculated caloric needs. As mentioned previously,

our standard feeding is Vivonex TEN® (1 kcal/cc and .038 gm protein/cc).

We start as a 1/2 strength dilution to decrease osmotic diarrhea. The rate and

concentration are advanced to meet the caloric needs as tolerated.

Diarrhea is a common problem in tube fed patients. Diarrhea is generally defined

by the volume of output, with > 1500 cc (30 cc/kg)/day as diagnostic. The

reasons for diarrhea are multiple and include altered gut flora associated with

antibiotic use, continuous feedings, and the osmolarity of the feedings. Measures

that should be taken when diarrhea is encountered include the following:

1. Check for Clostridium difficile colitis by examining the stool for toxin

and treating with oral flagyl or vancomycin.

2. Include bulk in the tube feedings by adding psyllium (Metamucil®)

3. Add Bacid® to alter the microflora

4. Decrease the osmolarity of the feedings by adding water to the formula.

The infused volume must increase to meet the calculated caloric

demands.

Table 6.3. Tips helpful in the placement of nasoduodenal tubes

Right lateral decubitus position for 2 h

Use of prokinetic medications such as

• Metoclopramide

• Cisapride

• Erythromycin

Use of bedside fluoroscopy

Use of endoscopy

Always check for adequate position with radiological studies.

TRANSITIONING TO REGULAR DIET

Burn patients should be given a regular diet as soon as it is tolerated. The transition

from tube feedings to regular PO intake is slow and may take several days to

weeks. The following steps are useful in achieving this goal:

1. Reduce tube feedings accordingly, as the PO intake increases (the sum

should be 100% of the goal assessed)

2. Consider only nocturnal tube feedings with a daytime regular diet.

3. When the PO intake is 50% of the goal, begin a 3 days trial of PO only.

Oral fluid administration should be controlled. Burn patients are susceptible

to hyponatremia if oral fluid intake is uncontrolled. At our hospitals, we follow

guidelines for juice/soda intake (see Table 6.4). The general concept is to give only

fluids that have caloric value, avoiding the excessive amount of free water in order

to minimize the presence of hyponatremia.

Frequent assessment of the burn patient is needed to ensure that enteral nutrition

support is being tolerated and that nutritional goals are met. Body weight,

fluid intake and output, serum electrolytes, blood glucose, BUN, creatinine, calcium, phosphorus and magnesium are monitored daily, prealbumin and liver enzymes

twice weekly, and 24 h total urinary urea nitrogen weekly. These laboratory

tests are important to give an objective assessment of metabolic homeostasis expected

to be achieved with the nutritional support. Improved serum protein tests

and nitrogen balance indicate an adequate protein caloric state.

Table 6.4. Recommendations for juice/soda intake in pediatric acute burns

Age Juice Soda Time period

0-1 year 0 0 24 h

1-4 years 60 cc/8h (180cc) 0 24 h

5-10 years 100 cc/8 h (300cc) 60 cc/8 h (180cc) 24 h

SUMMARY

The hypermetabolic response in burn patients can be as high as 200% the

normal metabolic rate. The goals of adequate nutritional support are to maintain

and improve organ function, prevent protein-calorie malnutrition, and improve

outcomes in general. The optimal dietary composition contains protein at about

1-2 gm/kg/day, with a calorie to nitrogen ratio around 100:1. Fatty liver is common

after severe burns. For this reason we prefer to use carbohydrate-based

feedings, excluding the use of excessive lipids. Enteral administration of feedings

is recommended over parenteral feedings because it is more physiologic, less costly,

maintains gut function and has less severe complications. Frequent assessment of

the burn patient is required to ensure that nutritional goals are met. Burn patients

should be given regular diet as soon as it is tolerated.

REFERENCES

1. Herndon DN, Curreri PW. Metabolic response to thermal injury and its nutritional

support. CUTIS 1978; 22 (4):501-506, 514.

2. Yarborough MF, Herndon DN, Curreri PW. Nutritional management of the severely

injured patient; (1) Thermal injury. Comtep Surg 1978; 13:15-20.

3. Hildreth MA, Herndon DN, Desai MH, Duke MA. Reassessing caloric requirements

in pediatric burn patients. J Burn Care Rehabil 1988; 9(6): 616-618.

4. Hildreth MA, Herndon DN, Desai MH, Broemeling LD. Caloric requirements of

patients with burns under one year of age. J Burn Care Rehabil 1993; 14:108-112.

5. Waymack JP, Herndon DN. Nutritional support of the burned patient. World J

Surg 1992; 16:80-86.

6. Herndon DN, Barrow RE, Stein M, Linares H, Rutan TC, Rutan RL, Abston S.

Increased mortality with intravenous supplemental feeding in severely burned

patients. J Burn Care Rehabil 1989; 10(4):309-313.

7. Herndon DN, Morris SE, Coffey JA Jr, Milhoan RA, Barrow RE, Traber DL,

Townsend CM. The effect of mucosal blood flow on enteric translocation of

microorganism in coetaneous thermal injury. Prog in Clin Biol Res 1989;

308:201-206